Agreed at the 25th meeting of the Nuclear Science Committee [NEA/SEN/NSC(2014)2]

Modified (election of the Chair) at the 26th meeting of the Nuclear Science Committee [NEA/SEN/NSC(2015)2]

Extended and revised at the 27th meeting of the Nuclear Science Committee in June 2016 [NEA/SEN/NSC(2016)2]

Discussed at the 29th meeting of the Nuclear Science Committee in June 2018 [NEA/SEN/NSC(2018)6]

Mandate of the Expert Group on Multi-physics Experimental Data, Benchmarks and Validation (EGMPEBV) [NEA/SEN/NSC(2018)10]

Mandate (Document extract):

Extract from document [NEA/SEN/NSC(2018)10]

Introduction

The processes for performing experiments, creating benchmarks and standard problems, and using these data to validate computer codes, have been developed and implemented for several decades, with highly satisfactory results for most standard applications. Nevertheless, the global context of nuclear technology development continues to evolve and new challenges to the status quo have been appearing:

The development of coupled “multi-physics” codes that allow for higher fidelity in the representation of the physical phenomenology and also allow for explicit representations of coupling phenomena. Validation of these new capabilities will require access to data that are representative of the depth of the modeling and of the coupling phenomena.

Associated with a move to best-estimate methods in safety analyses, there is often a requirement for increased rigor in the validation process, particularly in the estimation of uncertainties.

The availability of experimental facilities and associated skills capabilities have continued to decline in many countries, resulting both in the potential loss of valuable data and making reproducibility checks and fully independent peer review more difficult. For some applications there is therefore a risk of systematic biases in experimental analyses. The preservation of data with documentation is, therefore, essential.

A common bank of certified data for clearly defined applications will save resources of vendors and regulators.

Scope

Under the guidance of the Nuclear Science Committee (NSC), the Expert Group will deal with the activities associated with the certification of experimental data and benchmark models along with establishing the processes and procedures for using the data and benchmark models for validation of multi-physics modelling and simulation tools and data.

Objectives

The objectives of the Expert Group are the following:

to provide member countries with the guidance and processes for certifying experimental data for its use as a benchmark or for uses as general testing of multi-physics modelling and simulation tools;

to provide member countries with access to evaluated experimental data from the contributions of individual member countries;

to provide member countries with guidance and recommendations for developing benchmark models from certified experimental datasets;

to provide member countries with access to standardized benchmark models with detailed uncertainty evaluations and uncertainty methodology guidelines;

to provide member countries with recommendations and guidelines for the range of applicability of the certified experimental datasets;

to provide member countries with guidelines and consensus recommendations for validating multi-physics simulations; and

to provide member countries with demonstrations of the validation recommendations for specific industrial challenge problems.

Links to other NEA working parties

The expert group will liaise closely with other relevant NEA working parties and expert groups, including those operating under the guidance of the NSC and the Committee on the Safety of Nuclear Installations (CSNI), to ensure that the respective programmes are complementary and to provide advice and support where required and undertake common work where appropriate.

Deliverables

The deliverables of the Expert Group are the following:

a summary report of the status of experimental facilities in NEA member countries for thermal-hydraulic and fuel performance experiments needed for multi-physics validation;

a report on the metrics and processes for certifying experimental data intended for use in validation of multi-physics M&S tools and data;

a report on the metrics and processes for developing benchmark models from certified experimental data;

the development of a thermal hydraulics database for use in multi-physics benchmarking activities;

the development of a database of evaluated experimental multi-physics data;

the development of a database of evaluated multi-physics benchmark models;

a report on the guidelines and applicability of certified data and benchmark models for validation of M&S tools and data with application specific examples; and

a summary report on the validation exercise for pellet cladding mechanical interaction.